Aircraft collision warning system

ABSTRACT

An aircraft collision warning system includes an optical detection system has a toroidal and conical field of view about the aircraft to detect near objects. The detection system utilizes thermal detection in a passive mode. Optionally, the detection system also includes radio frequency (RF) elements to form a directional radar for improved object detection confidence. The radar is used in either a passive or active mode. The detection system includes a detector array to detect light from the toroidal-shaped and conical-shaped airspace. Data from the detector array is accumulated and analyzed for objects. Upon object detection, the object is tracked, kinetically assessed for collision with the aircraft, and reported to the pilot and/or auto-pilot system. The detection system is configured as a non-cooperative system that stares into the toroidal and conical field of view.

FIELD OF THE INVENTION

The invention relates to a method and apparatus for detecting thepresence of objects in a defined space. In particular, the inventionrelates to a method and apparatus for detecting near objects andrelative positions.

BACKGROUND OF THE INVENTION

Conventional aircraft collision avoidance systems are cooperative innature. Each aircraft includes a transponder that transmits a detectablesignal providing identification and positioning information to otheraircraft and ground based systems. Aircraft and ground based systemsreceive this transmitted data for all aircraft in a defined area andgenerate a three-dimensional map indicating the aircraft positions.

Most aircraft also include a radar system. Radar is a system that useselectromagnetic waves to identify the range, altitude, direction, orspeed of both moving and fixed objects such as aircraft, ships, motorvehicles, weather formations, and terrain. A radar system has atransmitter that emits either radio waves or microwaves that arereflected by the target and detected by a receiver, typically in thesame location as the transmitter. Although the signal returned isusually very weak, the signal can be amplified. This enables radar todetect objects at ranges where other emissions, such as sound or visiblelight, would be too weak to detect. Radar is used in addition tomonitoring transponder signals. Radar is effective in all weatherconditions, but requires significant effort to focus. As such, radar isuseful for determining range and bearing, but is not particularly usefulfor determining precise size and definition.

SUMMARY OF THE INVENTION

Embodiments of the present invention are directed to an apparatus forand a method of protecting an aircraft from collisions. A detectionsystem has a toroidal field of view about the aircraft to detect nearobjects. In some embodiments, the detection system also has a conicalfield of view below the aircraft. In some embodiments, the detectionsystem utilizes thermal detection. Optionally, the detection system alsoincludes radio frequency (RF) elements to form a directional radar forimproved object detection confidence. The RF elements are positioned onan outside surface of a detection system housing. The detection systemincludes a detector array to detect light from the toroidal-shaped andconical-shaped airspace. Data from the detector quay is accumulated andanalyzed for objects. Upon objet detection, the objects are tracked,kinetically assessed for collision with the aircraft, and reported tothe pilot and/or auto-pilot system.

The detection system is configured as a non-cooperative system thatstares into a toroidal and conical field of view about the aircraft. Asused herein, a “non-cooperative” object refers to an object that doesnot purposely transmit its position, as in a transponder. As also usedherein, “staring” refers to using stationary optics. Staring does notinclude optical components that move, pan, tilt, or rotate to scanacross a field a view. In some embodiments, the detection system ispassive, where the detection system detects near-object thermal energyand spurious EM (electro-magnetic) energy coming at the aircraft. Inother embodiments, the detection system is configured for activedetection. In this case, the detection system includes radar fortransmitting outbound signals and monitoring for resulting reflectedinbound signals.

The detection system of collecting thermal energy is comprised of a setof novel shaped mirrors that collect light for the detector array andovercomes the obstruction of a housing that mechanically supports themirror segments to an aircraft fuselage.

The detection system is located on the under belly of the aircraft toview a defined space below and slightly above to detect near-objects. Asecond detection system can be added to the top surface of the aircraftto give a complete sphere of detection to the airplane. The housingincludes a novel cowling shape at the base of the support structure thatguides the high speed airflow around the mirror segments to maintain auniform temperature over the mirror segments. By maintaining an even airflow, the mirror does not contribute thermal noise as part of theoptical collection system.

The optional RF antenna elements are individually measured with respectto their received radiation intensity and phase to each other to achievea directional measurement of external EM that is likely generated from anearby aircraft.

These and other advantages will become apparent to those of ordinaryskill in the art after having read the following detailed description ofthe embodiments which are illustrated in the various drawings andfigures.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthis specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention but not limit the invention to the disclosed examples.

FIG. 1 illustrates an elevation view of an aircraft 10 and an exemplaryfield of view covered by a detection system 100 of the presentinvention.

FIG. 2 illustrates a cut-out side view of an exemplary configuration ofthe detection system 100.

FIG. 3 illustrates a perspective view of the mirror segments 101, 102.

FIG. 4 illustrates a bottom-up view of the mirror segments 101, 102.

FIG. 5 illustrates one of the mirror segments including a thermalelectric cooler (TEC).

FIG. 6 illustrates a cut-out side view of an alternatively configuredmirror segment assembly.

FIG. 7 illustrates a bottom up view of the mirror segments 101, 102configured for passive and active RF signal detection.

FIG. 8 illustrates an exemplary configuration of a portion of the mirrorsegments 101, 102 including a plurality of facets.

FIG. 9 illustrates an exemplary system for calibrating the detectionsystem 100.

FIG. 10 illustrates an exemplary schematic block diagram of the systemprocessing assembly 114.

FIG. 11 illustrates an exemplary process for determining a potentialcollision with the aircraft.

The present invention is described relative to the several views of thedrawings. Where appropriate and only where identical elements aredisclosed and shown in more than one drawing, the same reference numeralwill be used to represent such identical elements.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

Reference will now be made in detail to the embodiments of the objectdetection and collision avoidance system of the invention, examples ofwhich are illustrated in the accompanying drawings. While the inventionwill be described in conjunction with the embodiments below, it will beunderstood that they are not intended to limit the invention to theseembodiments and examples. On the contrary, the invention is intended tocover alternatives, modifications and equivalents, which may be includedwithin the spirit and scope of the invention as defined by the appendedclaims. Furthermore, in the following detailed description of thepresent invention, numerous specific details are set forth in order tomore fully illustrate the present invention. However, it will beapparent to one of ordinary skill in the prior art that the presentinvention may be practiced without these specific details. In otherinstances, well-known methods and procedures, components and processeshave not been described in detail so as not to unnecessarily obscureaspects of the present invention.

Some portions of the detailed descriptions which follow are presented interms of procedures, logic blocks, processing, and other symbolicrepresentations of operations on data bits within a computer system andmemory or over a communications network. These descriptions andrepresentations are intended to most effectively describe to thoseskilled in the data processing arts to convey the substance of theinvention. A procedure, logic block, or process is here, and generally,conceived to be a self-consistent sequence of steps or instructionsleading to a desired result. The term computing system is used herein asa digital arithmetic integrated circuit comprised of memory, a centralprocessing unit and interface logic. The operation is from algorithmsand rules stored in non-volatile memory to measure the sensors, computea result and take an action. This is often referred to as an embeddedsystem. Although reference to a computing system is used, it isunderstood that application of the described methods can be similarlyapplied using any similar electronic device.

FIG. 1 illustrates an elevation view of an aircraft 10 and an exemplaryfield of view covered by a detection system 100 of the presentinvention. The detection system 100 is coupled to an underside ofaircraft 10. Light enters an active panoramic area of the detectionsystem 100 through an angle 360° in azimuth and a first angle 4 abovethe horizon 2 and a second angle 6 depressed below the horizon 2. Theresulting toroidal field of view, or toroidal-shaped airspace, isdefined by an upper boundary 14, as defined by the first angle 4, and alower boundary 16, as defined by the second angle 6. An outer bound ofthe toroidal-shaped airspace is defined by an optical assembly includedwithin the detection system 100. In some embodiments, the first angle 4is 5° and the second angle 6 is 30°. Alternatively, the first angle 4and the second angle 6 are any angles configured according to a mirrorsegment assembly within the detection system 100. The mirror segmentassembly is shaped in such a way as to map the airspace into a detectorarray preserving equal, or otherwise predetermined, pixel resolution foreach angle of elevation, or declination, within a toroidal-shapedairspace.

The active panoramic area of the detection system 100 also includes aconical field of view below the aircraft. This conical-shaped airspaceis defined by conical boundary 18, which is defined by cone angle 8about horizon normal 12. In some embodiments, the cone angle 8 is 12°.Alternatively, the cone angle is any angle configured according to themirror segment assembly within the detection system 100.

Within the toroidal and conical field of views shown in FIG. 1, there isnot 100% coverage around the aircraft at any given moment. However, dueto the dynamics of a moving aircraft, some of the airspace not coveredby the toroidal and conical field of view at one instant is covered in anext instant by the movement of the aircraft. In this case, the delay isrelated to the speed and attitude (pitch, roll, yaw rates) of theaircraft in combination with the dynamics of any detected object.

FIG. 2 illustrates a cut-outside view of an exemplary configuration ofthe detection system 100. The detection system 100 includes a mirrorsegment assembly and a housing 104. The mirror segment assembly includesmultiple mirror segments, struts 130, and a fairing 120. In theexemplary configuration shown in the following figures and describedbelow, the mirror segment assembly includes two mirror segments 101 and102. The struts 130 are coupled to the housing 104 and to the fairing120. The detection system 100 is coupled to the aircraft 10 by thestruts 130. The fairing 120 supports the mirror segments 101, 102, andholds the mirror segments 101, 102 in place relative to the aircraft 10.The struts 130 include a circular airfoil 132 (also see FIG. 7) at thebase of the struts 130 to deflect the airflow out of the path of themirrors segments 101, 102, thereby maintaining a stable flow field thatreduces temperature fluctuations at the surface of each mirror segment101, and keeping each mirror segment 101, 102 clean.

Light reflecting from the mirror segments 101, 102 enters the housing104 through a bezel and lens 105, reflects off a stationary mirror 106,into a lens 108, and impinges onto a detector array 110, where signalelectronics also reside. In some embodiments, the bezel 105 isconfigured as a flat Germanium bezel. Optionally, included in thehousing 104 is an inertial measurement unit (IMU) 112 and a systemprocessing assembly 114. The system processing assembly 114 includes asystem processor and other related electronics, as described in greaterdetail below. In some embodiments, the area within the housing 104 issealed such that a desired environment can be created. In one exemplaryapplication, a nitrogen environment is created within the housing 104.

The mirror segments 101, 102 are configured such that light from withinthe toroidal-shaped airspace, as defined by the boundaries 14 and 16, isreflected through the bezel 105. Each mirror segment 101, 102 can alsobe configured such that when assembled an opening 118 is formed at anapex of the mirror segments 101, 102, which is located closest to thebezel 105. The opening 118 enables light to enter the bezel 105 from theconical-shaped airspace below the aircraft 10, as defined by the conicalboundary 18. To enable light to pass up through the opening 118, thefairing 120 can be configured in a shape similar to the assembled mirrorsegments 101, 102, with a matching opening to the opening 118. In someembodiments, a lens is positioned within the opening 118. The lens isconfigured to provide the cone angle of the conical field of view belowthe aircraft 10.

FIG. 3 illustrates a perspective view of the mirror segments 101, 102.FIG. 4 illustrates a bottom-up view of the mirror segments 101, 102. Thearrows impinging the mirror segments 101, 102 in FIG. 4 represent lightrays. Although not shown in FIGS. 3 and 4, the struts 130 (FIG. 2) arepositioned in the gap between the mirror segments 101, 102, at the endof the mirror segments opposite the opening 118. The position of thestruts 130 is represented by a strut center-line in FIG. 4. The mirrorend 134 of the mirror segment 101 and the mirror end 136 of the mirrorsegment 102 are curved such that each mirror segment 101, 102 reflectslight from a panoramic field of view greater than 180°. Thisconfiguration enables light to be collected from around the struts 130,thereby giving an uninterrupted 360° panoramic field of view. In otherwords, the shape of the mirror segments 101, 102 near the intersectionof the struts 130 are curved in such a way as to enable light rays 138and 140 to enter the detector array 110 (FIG. 2) that would normally beobstructed by the struts 130. Although the shape of the mirror segments101, 102 provides a 360° panoramic field of view, there is a dead space166 proximate the detection system 100 within which light is notdetected. However, the dead space 166 covers a relatively small volumeof airspace, extending only a few feet from the detection system 100.

In general, the configuration and shape of the mirror segments 101, 102provide at least the following important features. First, lightdetection from the airspace is directed around the struts, so that thereis no occlusion of light due to the struts. Second, the mirror segmentscan include facets, as described in detail below. Third, the mirrorsegments can linearly or non-linearly provide sterpixels of light intothe detector array. Linear distribution provides uniform pixel detectionin elevation and azimuth. Non-linear distribution provides non-uniformpixel detection, for example a greater number of sterpixels are gatheredfrom at or near the horizontal plane, and fewer sterpixels are gatheredaway from the horizontal plane. Such mirror segment configurationredistribute the detectors in azimuth and/or elevation.

The struts 130 are positioned within the dead space 166, and as such,the struts 130 do not obstruct the toroidal field of view monitored bythe detection system 100. The mirror segments 101, 102 and the struts130 are oriented such that the strut center-line is aligned with theforward direction of the aircraft. The struts 130 are also narrowlyconfigured through the direction of airflow.

In some embodiments, the detection system 100 is configured for thermaldetection. In this case, the bezel 105 and the lens 108 are configuredto pass long wave infrared (LWIR) light and the detector array 110 isconfigured to detect LWIR light. In some configurations, the outersurfaces of the mirror segments 101, 102 are coated with an efficientreflective coating, with high reflectance and low optical distortion,for LWIR light, and the mirror segments 101,102 are made from an alloyaluminum substrate. In general, the detection system 100 can beconfigured to detect any desired light wavelength, and the mirrorsegments, lenses, mirrors, and detector array are configured to directand detect the desired light wavelength.

In some embodiments, the inside, or concave, surface of the mirrorsegments 101, 102 is evenly temperature chilled as a means to improvethe LWIR image quality. FIG. 5 illustrates a portion of one of themirror segments including a thermal electric cooler (TEC). The substrateof each mirror segment 101, 102 is cooled by a TEC 144 and controlled bya temperature monitoring and actuation circuit 146. The circuit 146 canbe included in the system processing assembly 114 (FIG. 2), or thecircuit 146 can be a stand-alone circuit. In an exemplary application,the mirror segments 101, 102 are temperature controlled to limit thenoise generated by temperature fluctuations in the mirror segments.

In general, the fairing 120 functions to divert airflow past the mirrorsegments 102, 102 and also functions as a structural element to couplethe struts 130 to the mirror segment assembly. In some embodiments, thefairing 120 (FIG. 2) extends into the interior of the mirror segmentassembly to provide structural support to the mirror segments 101, 102.The fairing 120 can be shaped similarly to an upside down cup with ahole at its bottom. The fairing 120 can be a framework or a solid form.In other embodiments, the fairing 120 only extends partially into themirror segment assembly, or is positioned substantially at the widestdiameter of the mirror segment assembly with little if any extensioninto the interior of the mirror segment assembly. Where the fairing 120is configured as a cup-like structure, the shape of this “cup” issimilar to the shape of the assembled mirror segments 101, 102. A wideend of the cup is coupled to the struts 130, and the hole in the cup isaligned to the opening 118 in the mirror segments 101, 102. In thisconfiguration, the fairing 120 (FIG. 2) does not block the light fromthe conical-shaped airspace below the aircraft 10 from passing throughthe opening 118 into the bezel 105 (FIG. 2). In other embodiments, thefairing 120 blocks some or all of the light from the conical-shapedairspace from passing through the opening 118. In this case, additionaloptical elements are included to direct light from a substantiallysimilar conical-shaped airspace outside the diameter of the mirrorsegments 101, 102 and through the bezel 105.

FIG. 6 illustrates a cut-out side view of an alternatively configuredmirror segment assembly. Mirrors 152 and 154 direct light from aconical-shaped airspace outside the diameter of the mirror segments101′, 102′ and through the bezel 105. In some embodiments, the mirror152 is positioned outside the apex of the mirror segments 101′ 102′. Inthis case, there is no need for the opening 118. In other embodiments,as shown in FIG. 6, the mirror 152 is positioned in the interior of theassembled mirror segments 101′, 102′. In this case, the opening 118′ isconfigured to allow light to be reflected from the mirror 154, throughthe opening 118′, to the mirror 152, and back out the opening 118′ tothe bezel 105.

The detection system 100 is configured as either a single-mode detectionsystem or a multiple-mode detection system. As a single-mode detectionsystem, the detection system detects a defined range of lightwavelengths, such as long wave infrared light, using an opticaldetection system that includes the mirror segment assembly and detectorarray. As a multiple-mode detection system, there is sensitivity to aspectrum of electromagnetic energy. Differently defined ranges such asLWIR or visible light and RF energy collection are known appliedscience. The LWIR light is detected using the mirror segment assemblyand detector array, and the RF energy is detected using an RF antennaassembly. In some embodiments, the detection system is configured forpassive detection, also referred to as “listen only”, where thedetection system detects spurious EM energy, such as LWIR light or RFlight, coming at the aircraft. In other embodiments, the detectionsystem is configured for passive and active detection, also referred toas “broadcast”. In this case, the detection system also includes an RFtransmitter that actively transmits RF signals. The detection systemconfigured in this manner passively detects spurious EM energy as wellas actively detects reflected RF signals.

In some embodiments, individual RF antenna elements within the RFantenna assembly can be individually tuned to adjust their respectivephases, thereby forming a single conceptual receiver configured todetect RF signals from a computer controlled direction.

FIG. 7 illustrates a bottom up view of the mirror segments 101, 102configured for passive and active RF signal detection. An array of RFantenna elements 148 and an RF transmitter 150 are coupled to thefairing 120 to form a phased RF transceiver. It is understood that thefairing 120 can be configured for only passive RF signal detection. Inthis case, the RF transmitter 150 is removed.

Although the multiple-mode operation is described as detecting RFsignals, it is understood that other wavelength signals can be detected,such as micro-wave signals. In this case, the RF antenna elements arereplaced by microwave antenna elements, and the RF transmitter isreplaced by a microwave transmitter.

The detector array 110 includes a plurality of detectors, each detectordetects a pixel of light across a defined solid angle. Any pixelorientated system is a quantized system. The more pixels, the morecontinuous the data appears. In one method of distribution, the mirrorsegments 101, 102 are configured to provide a substantially uniformcoverage of the toroidal-shaped airspace and the conical-shaped airspacemonitored by the detection system 100. In another method, a detectionsignal-to-noise ratio is improved by grouping many detectors through asmall sterpixel volume, where a sterpixel is the solid angle of lightcoming from the volume that impinges a specific detector. FIG. 8illustrates an exemplary configuration of a portion of the mirrorsegments 101′, 102′ including a plurality of facets. Facets 156 arefabricated on the mirror segments 101′, 102′, where each facet is a flator curved face on the outer surface of the mirror segment and forms eachsmall sterpixel volume. Each facet enables a group of detectors todetect light from substantially the same airspace, thereby quantizingthe signal detection over many detectors. This configuration improvesthe signal-to-noise ratio per group of sterpixels, but reduces theoverall volume of airspace imaged.

Facets can be formed by micro-machining. Using facets on the mirrorsegments in this manner, the aircraft 10 is surrounded by ‘porky pinespikes’ of detection zones, each spike corresponding to a facet. Thesignals from the group of photo detectors associated with each facet 156are analyzed by the system processor to determine if a detectionthreshold has been met, thereby indicating a ‘near-object’ is present.Although FIG. 8 shows facets fabricated on only a portion of the mirrorsegments 101′, 102′, it is understood that facets can be fabricated onany or all surfaces of the mirror segments 101′, 102′ and can havedifferent individual shapes and sizes.

In order for the detection system 100 to accurately determine a positionof any detected object, the detection system 100 is calibrated and atranslation table is generated. FIG. 9 illustrates an exemplary systemfor calibrating the detection system 100. The detection system 100 isplaced in the center of a calibration chamber 160. The detection system100 is coupled to a computing device 164 to send sensor data collectedby each of the detectors in the detector array 110 (FIG. 2). Emitters162 are positioned on the inner surface of the calibration chamber 160.In some embodiments, emitters cover the entire inner surface of thecalibration chamber. In other embodiments, emitters are placed only onthose portions of the inner surface that correspond to the definedtoroidal field of view and the conical field of view to be monitored bythe detection system 100. FIG. 9 shows only a portion of the emitters162. Each of the emitters 162 is coupled to the computing device 164.The computing device 164 initiates an emitter activation sequence bywhich each emitter 162 is independently activated, one at a time. Theresponse of the detector array 110 is measured upon each emitteractivation. The size of the calibration chamber 160 and the size of eachof the emitters 162 are configured such that each emitter 162 is asingle sterpixel corresponding to each detector in the detector array110. The mirror segments 101, 102 are formed in such a way that theoptical system allows each detector to collect light within a uniquesterpixel, where each sterpixel corresponds to a specific segment of themonitored airspace. These segments can be distributed linearly ornon-linearly through the airspace. As such, there should be a one-to-onerelationship between each detector and each sterpixel in space, asrepresented by a specific emitter 162. The calibration processdetermines if there are any non-monotomic responses of the detectorarray, meaning that a single detector should not detect light emittedfrom two or more different emitters 162, which represents two or moredifferent sterpixels in space.

Further, for the detection system 100 to determine an accurate positionof a detected object, the detection system 100 calculates positionaldata according to a predefined coordinate system. This coordinate systemdefines an optimal theoretical relationship between each detector and acorresponding sterpixel location in space that the detector measures.According to this theoretical mapping, each detector should detect lightemitted from a single specific emitter position, for example detector Adetects light emitted by emitter A. The calibration methodexperimentally determines an actual relationship between detectors andsterpixels. If it is determined that detector A instead detects lightemitted from emitter B, a translation is calculated that compensates forthe difference between the position of emitter B and the position of theemitter A. In this manner, a translation table is generated for each ofthe detectors in the detector array 110 so that when light is detected,an actual position of any detected object is determined. The translationtable is stored in system memory 208 (FIG. 10). Such a calibrationcorrects for fabrication errors in the mirror segments and/or thedetectors, as well as for installation alignment errors of the mirrorsegments when initially installed in the system.

FIG. 10 illustrates an exemplary schematic block diagram of the systemprocessing assembly 114. The system processing assembly 114 computesbackground, moving objects, inertially compensates the objects,calculates kinetic trajectories of interference risk, and communicateswith outside systems. The system processing assembly 114 controls andinterfaces with the detector array 110 and the IMU 112, integrates thecollected data, and determines various characteristics of the airspacearound the aircraft 10. The IMU 112 generates spatial reference datathat is used by the system processing assembly 114 to establish a worldcoordinate of objects detected by the detector array 110 or radar 148.In some embodiments, the IMU 112 is part of the aircraft electronics andis external to the system processing assembly 114. In other embodiments,an IMU is included in the system processing board of the detectionsystem.

Pixel data collected by the detector array 110 is either digitized by acommon frame-grabber 202 or if the pixel data is already digitized bythe detector array 110, the digital pixel data is read by a low voltage,differential signal receiver (LVDS) 204. The digital pixel data isprovided to a field programmable array (FPGA) 206. In some embodiments,the frame grabber 202 and the LVDS 204 are part of circuitry inside theFPGA 206. The FPGA 206 performs realtime spatial sterpixel re-mapping toovercaom all optical system errors. Detector data is input at a variablerate, typically at a 30 Hz frame rate.

As pixel data enters the FPGA 206, it is directed to a buffer inexternal memory 210. The location in the buffer is determined by there-mapping process using the translation table 208. The resultant bufferof sterpixels in memory 210 is addressed as a uniform toroid about theaircraft 10. In the case where facets 156 (FIG. 8) are used, the bufferof sterpixels in memory 210 is addressed as a progression of spikeswithin the toroid-shaped airspace about the aircraft 10.

The system processor 212 reads the aircraft referenced sterpixels frommemory 210 and takes data from the IMU 112 and computes stabilizedspatial awareness according to Earth coordinates. In this manner, theprocessor re-maps the sterpixel data from an aircraft reference to anEarth reference. The processor 212 determines object presence andtrajectory from multiple, time-separated, detector data and theaircraft's kinetic motions to achieve spatial stable tracking of foreignobjects. From the analysis of the foreign object, the level of threat isdetermined for annunciation to the aircraft avionics and pilot. Thesystem processor 212 interfaces to the aircraft avionics through theAvionics Standard Communications Bus 214 protocol. An additionalcommunication path is provided for redundancy and technical support by aRS422 serial interface 216.

FIG. 11 illustrates an exemplary collision avoidance process. At thestep 300, pixel data collected by the detector array 112 is input to theFPGA 206 at some variable frame rate. The pixel data from all detectorsrepresents a complete instantaneous field of view, referred to as aframe. In this exemplary application, the frame rate is thirty frames asecond (30 Hz). As previously described, the field of view includes thetoroidal field of view around the aircraft and the conical field of viewbelow the aircraft. Each detector in the detector array is mapped to aspecific volumetric geometry, sterpixel, during the factory calibrationprocedure, thereby resulting in the aforementioned translation table. Atthe step 301, the translation table is retrieved from memory 208. At thestep 302, current inertial data of the aircraft 10 is retrieved from theIMU 112. At the step 303, the new frame of detector measurementsreceived at the step 300 is compensated for spatial location by thetranslation table received at the step 301, and the new frame iscompensated according to the current inertial data received at the step302, thereby forming an Earth-referenced frame. The Earth-referencedframe is stored in an image buffer organized in the system memory as auniform and geo-located detection zone surrounding the aircraft. Thedetection zone includes the toroidal-shaped airspace and theconical-shaped airspace.

At the step 304, the system processor 212 computes and maintains anormal, or background, value for each detector and groups of detectors.If an object is present in the monitored airspace, the object may bedetected by one or more detectors, depending on the size of the objectand on the distance between the object and the aircraft. For example, anobject positioned near an outer range of the detection airspace may bedetected only be a single detector. As that same object moves closer tothe aircraft, multiple adjacent detectors may detect the object. Thebackground is computed as a running, weighted average of pastEarth-referenced frame measurement values.

At the step 305, for each new Earth-referenced frame generated at thestep 303, the new Earth-reference frame is compared to the backgrounddata computed at the step 304. Comparison is made on a detector bydetector basis, or on a group of detectors by group of detectors basis.In this manner, pixel data collected from a first detector, or firstgroup of detectors, is compared to background data corresponding to thesame first detector, or first group of detectors. At the step 306, it isdetermined if the comparison performed at the step 305 results in adifference that exceeds a predetermined threshold value. In the casewhere the thermal detector detects LWIR, there is a thermal differencebetween an object and the background. If it is determined at the step306 that the difference exceeds the predetermined threshold, then at thestep 307 it is determined that either a new object is present in thecorresponding airspace or a previously detected object has moved. Alocation of the detected object is recorded along with an internalidentification. If it is determined at the step 306 that the differencedoes not exceed the predetermined threshold, then at the step 308 it isdetermined that either no new object is present in the correspondingairspace or a previously detected object is still present in thecorresponding airspace.

At the step 309, existing objects have their location, direction,velocity, and acceleration computed at each iteration of this process.These computations use the data from the IMU to determine the object'srelative interaction with the aircraft. At the step 310, it isdetermined if the object is going to collide with the aircraft. Thisdetermination is made using the object dynamics calculated at the step309 and the current aircraft dynamics, collectively referred to ascollision metrics. If it is determined at the step 310 that a collisioncondition exists, then at a step 311, this condition is communicated tothe pilot, auto-pilot, or the aircraft's self defense system. If it isdetermined at the step 310 that a collision condition does not exist,then at a step 312 the current iteration of the collision avoidanceprocess ends and the next iteration of the collision avoidance processbegins at the step 300.

The detection system is described above as including a reflectiveoptical component, such as the mirror segments 101, 102, to reflectlight to a lens and detector array. In an alternative embodiment, thereflective optical component is replaced with a fisheye lens. Light iscollected by the fisheye lens over a panoramic field of view rangingthrough an angle 360° in azimuth and an angle above the horizon 2, suchas the first angle 4. This eliminates the need for a support system,such as the fairing 120 and the struts 130. In some embodiments, RFantenna elements are positioned around the fisheye lens. In still otherembodiments, RF transmitters in addition to the RF antenna elements arepositioned around the fisheye lens.

Although the object detection and collision avoidance system isdescribed in terms of an aircraft while in flight, the system can alsobe used for detection objects and avoiding collisions while the aircraftis on the tarmac, either moving or parked. The object detection andcollision avoidance system can also be used in applications other thanaircraft related, including but not limited to, surveillance and alarmsystems for detecting intruders.

The present invention has been described in terms of specificembodiments incorporating details to facilitate the understanding of theprinciples of construction and operation of the invention. Suchreference herein to specific embodiments and details thereof is notintended to limit the scope of the claims appended hereto. It will beapparent to those skilled in the art that modifications may be made inthe embodiment chosen for illustration without departing from the spiritand scope of the invention.

What is claimed is:
 1. An apparatus comprising: a. a detector arrayconfigured to detect long wave infrared light; b. an optical assemblyconfigured to direct light received from a toroidal-shaped airspacesurrounding an aircraft to the detector array, wherein the opticalassembly comprises a plurality of mirror segments coupled to an exteriorof the aircraft; c. a plurality of struts configured to couple theplurality of mirror segments to the exterior of the aircraft; and d. aprocessor configured to receive pixel data corresponding to the detectedlong wave infrared light from the toroidal-shaped airspace and todetermine collision metrics corresponding to non-cooperative objectswithin the toroidal-shaped airspace according to the detected long waveinfrared light.
 2. The apparatus of claim 1 further comprising a radarantenna to receive radio frequency signals, and the processor isconfigured to determine collision metrics according to the detectedradio frequency signals.
 3. The apparatus of claim 2 further comprisinga radar transmitter configured to output a radio frequency signal fromthe apparatus.
 4. The apparatus of claim 1 wherein the optical assemblyis further configured to detect long wave infrared light from aconical-shaped airspace below the aircraft.
 5. The apparatus of claim 1wherein the plurality of mirror segments are configured to reflect lightto the detector array through an angle 360 degrees in azimuth.
 6. Theapparatus of claim 1 wherein each mirror segment is separated from eachother mirror segment.
 7. The apparatus of claim 1 wherein a shape ofeach of the plurality of mirror segments is configured to reflect lightreceived from the toroidal-shaped airspace to the detector array and toavoid occlusion of light received from the toroidal-shaped airspace bythe plurality of struts.
 8. The apparatus of claim 1 wherein theplurality of mirror segments comprises two mirror segments, and eachmirror segment is curved to reflect light to the detector array throughan angle greater than 180 degrees in azimuth.
 9. The apparatus of claim8 wherein the plurality of struts are positioned between the two mirrorsegments.
 10. The apparatus of claim 1 further comprising a fairingcoupled to the plurality of struts and to the plurality of mirrorsegments.
 11. The apparatus of claim 10 wherein the fairing is coupledto a non-exterior surface of each of the plurality of mirror segments.12. The apparatus of claim 1 wherein the plurality of mirror segmentsinclude an opening at an apex of the plurality of mirror segments,wherein long wave infrared light from a conical-shaped airspace belowthe aircraft is detected by the detector array through the opening. 13.The apparatus of claim 12 further comprising a lens positioned in theopening at the apex.
 14. The apparatus of claim 12 wherein the processoris further configured to determine collision metrics corresponding tonon-cooperative objects within the conical-shaped airspace according tothe detected long wave infrared light.
 15. The apparatus of claim 1wherein one or more of the plurality of mirror segments includes one ormore facets.
 16. The apparatus of claim 1 further comprising a thermalelectric cooler coupled to an interior surface of each mirror segment.17. The apparatus of claim 1 further comprising a system memoryconfigured to store a translation table, wherein the translation tableincludes position compensation data for each detector in the detectorarray to compensate for fabrication or alignment error.
 18. Theapparatus of claim 17 further comprising an inertial measurement unit tomeasure an inertial movement of the aircraft.
 19. The apparatus of claim18 wherein the processor is configured to determine the collisionmetrics using data corresponding to the detected long wave infraredlight, the translation table, and the inertial movement of the aircraft.20. The apparatus of claim 1 wherein the optical assembly comprises astaring-based optical system.
 21. The apparatus of claim 1 wherein theapparatus is configured to passively detect long wave infrared light.22. An apparatus comprising: a. a detector array configured to detectlong wave infrared light; b. an optical assembly configured to directlight received from a toroidal-shaped airspace surrounding an aircraftto the detector array, wherein the optical assembly comprises aplurality of mirror segments coupled to an exterior of the aircraft, theplurality of mirror segments include an opening at an apex of theplurality of mirror segments, wherein long wave infrared light from aconical-shaped airspace below the aircraft is detected by the detectorarray through the opening; c. a processor configured to receive pixeldata corresponding to the detected long wave infrared light from thetoroidal-shaped airspace and to determine collision metricscorresponding to non-cooperative objects within the toroidal-shapedairspace according to the detected long wave infrared light.
 23. Theapparatus of claim 22 further comprising a radar antenna to receiveradio frequency signals, and the processor is configured to determinecollision metrics according to the detected radio frequency signals. 24.The apparatus of claim 23 further comprising a radar transmitterconfigured to output a radio frequency signal from the apparatus. 25.The apparatus of claim 22 wherein the optical assembly is furtherconfigured to detect long wave infrared light from a conical-shapedairspace below the aircraft.
 26. The apparatus of claim 22 wherein theplurality of mirror segments are configured to reflect light to thedetector array through an angle 360 degrees in azimuth.
 27. Theapparatus of claim 22 wherein each mirror segment is separated from eachother mirror segment.
 28. The apparatus of claim 22 further comprising alens positioned in the opening at the apex.
 29. The apparatus of claim22 wherein the processor is further configured to determine collisionmetrics corresponding to non-cooperative objects within theconical-shaped airspace according to the detected long wave infraredlight.
 30. The apparatus of claim 22 wherein one or more of theplurality of mirror segments includes one or more facets.
 31. Theapparatus of claim 22 further comprising a thermal electric coolercoupled to an interior surface of each mirror segment.
 32. The apparatusof claim 22 further comprising a system memory configured to store atranslation table, wherein the translation table includes positioncompensation data for each detector in the detector array to compensatefor fabrication or alignment error.
 33. The apparatus of claim 32further comprising an inertial measurement unit to measure an inertialmovement of the aircraft.
 34. The apparatus of claim 33 wherein theprocessor is configured to determine the collision metrics using datacorresponding to the detected long wave infrared light, the translationtable, and the inertial movement of the aircraft.
 35. The apparatus ofclaim 22 wherein the optical assembly comprises a staring-based opticalsystem.
 36. The apparatus of claim 22 wherein the apparatus isconfigured to passively detect long wave infrared light.
 37. Anapparatus comprising: a. a detector array configured to detect long waveinfrared light; b. an optical assembly configured to direct lightreceived from a toroidal-shaped airspace surrounding an aircraft to thedetector array; c. a processor configured to receive pixel datacorresponding to the detected long wave infrared light from thetoroidal-shaped airspace and to determine collision metricscorresponding to non-cooperative objects within the toroidal-shapedairspace according to the detected long wave infrared light; and d. asystem memory configured to store a translation table, wherein thetranslation table includes position compensation data for each detectorin the detector array to compensate for fabrication or alignment error.38. The apparatus of claim 37 further comprising a radar antenna toreceive radio frequency signals, and the processor is configured todetermine collision metrics according to the detected radio frequencysignals.
 39. The apparatus of claim 38 further comprising a radartransmitter configured to output a radio frequency signal from theapparatus.
 40. The apparatus of claim 37 wherein the optical assembly isfurther configured to detect long wave infrared light from aconical-shaped airspace below the aircraft.
 41. The apparatus of claim37 wherein the optical assembly comprises a plurality of mirror segmentscoupled to an exterior of the aircraft.
 42. The apparatus of claim 41wherein the plurality of mirror segments are configured to reflect lightto the detector array through an angle 360 degrees in azimuth.
 43. Theapparatus of claim 41 wherein each mirror segment is separated from eachother mirror segment.
 44. The apparatus of claim 37 further comprisingan inertial measurement unit to measure an inertial movement of theaircraft.
 45. The apparatus of claim 44 wherein the processor isconfigured to determine the collision metrics using data correspondingto the detected long wave infrared light, the translation table, and theinertial movement of the aircraft.
 46. The apparatus of claim 37 whereinthe optical assembly comprises a staring-based optical system.
 47. Theapparatus of claim 37 wherein the apparatus is configured to passivelydetect long wave infrared light.